#robotics Logs

May 27 2022

02:55 PM MrCurious: does anyone know of a good solution for recording position on 4 quadrature encoders at once, ideally without using the host computer to do that task? be ideal if i could i2c or spi request status of wheels, and get back (4) 32 bit signed integers.
03:21 PM Tom_L: MrCurious, that's what the index channel is for
03:22 PM Tom_L: otherwise you count edges
03:22 PM MrCurious: yeah, i can do it on arduino for one... (have no index) pololu motors
03:23 PM Tom_L: https://www.youtube.com/watch?v=o8lezpJhfAo
03:23 PM Tom_L: i have quad code for the avr if you want it
03:23 PM MrCurious: i was just hoping to find something i can throw money at, so i can avoid having to do AVR isr on a port and cope with the deltas in a time efficient way, then export vis i2c or spi... TBH i am just not that good at c
03:23 PM Tom_L: you need 2 interrupts ideally
03:24 PM MrCurious: i can dedicate a full avr to it
03:24 PM MrCurious: and even a host serial port
03:24 PM MrCurious: yes i want it please very much
03:24 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/avr/atmega328/PCINT0/quadrature/
03:25 PM MrCurious: why not on git hub so john q public can find it via searching the hub
03:25 PM Tom_L: ideally you want an interrupt on each channel
03:25 PM Tom_L: because then we wouldn't be having this lovely conversation :)
03:25 PM MrCurious: or on one port, grab 8 bits in parallel, and do mask magic math to do counters in a fast way
03:26 PM Tom_L: a fpga would work too
03:26 PM Tom_L: probaby do quite a few on it
03:26 PM MrCurious: ideally Rpi/jetson could map 8 bit inputs to a single io command...
03:27 PM Tom_L: i forgot where i put the quad code for the fpga..
03:28 PM MrCurious: i mean 4wd rover seems pretty common. lots of motor drivers for that, but each motor is different, so synchronizing them to drive strait seems like something people would pay for. bet if you put boards to do this on tindi or some other funding sales site, it would move product
03:28 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/temp/xilinx/quadrature/
03:29 PM MrCurious: i would pay up to $100 for a small 4 encoder reader i could just plug in and querry use :D
03:29 PM Tom_L: heh
03:29 PM Tom_L: repeat that when rue is here and i bet he takes you up on it
03:30 PM Tom_L: how many cpr?
03:30 PM Tom_L: the one i was using was like 2000
03:30 PM Tom_L: 500 single
03:31 PM MrCurious: that i am not sure of... i imagine in speed racer mode, traction becomes unreliable, and would need magnetometer and CV mechanisms to drive strait...
03:31 PM MrCurious: so this is really only useful for like 10 inch per minute rotation rates with a 28:1 gearing
03:32 PM Tom_L: way back when.. the 68332 i played with would switch modes if it got too fast and just read the index until it slowed back down
03:32 PM MrCurious: kick starter! i bet this shit would fund...
03:32 PM Tom_L: go for it
03:33 PM * Tom_L goes back to what he was doing
03:33 PM MrCurious: i lack the skill, and the motivation. so far i am good at buying robot parts(buried in them now), doing simple poc tests, but never stitching it all together
03:33 PM MrCurious: but now i have an AGX orin on my desk, i feel compelled to get one actually working
03:33 PM * Tom_L gives MrCurious some thread
04:18 PM MrCurious: found it. seems "asic" was the magic missing word https://www.phidgets.com/?tier=3&catid=4&pcid=2&prodid=1199
05:52 PM rue_mohr: still need to know how many counts/rev
05:58 PM MrCurious: that is simple enough with tape...